Don't you just hate it when that drop-dead gorgeous 65/66 Mustang of yours won't start? Or when you turn on the radio and the turn signals start flashing? If you have any questions that you think I might be able to help you with, or, if I have posted something that still doesn't seem to be as clear as it could be, please feel free to ask.

Hello

There is a very large class of people that own 65/66 Mustangs that, as far as I can tell, anyway, have been, for the most part, ignored entirely. They don't really want that 100 pt. show car that is so nice and was soooo expensive that they're afraid to drive it, they also don't want to make their car capable of achieving warp factor three. They just want this car that they dearly love to be able to cruise around smoothly and reliably, without having it dump them out on the side of the road or have it start making weird noises or belching out big clouds of funky-smelling smoke. And I think, truth be told, that this is by far the largest class of Mustang owners. They take their car to some technician when what they actually need is a mechanic, and this, frequently, does not work out very well at all for the owner. They don't want to re-engineer the entire car, they just want someone to fix what broke. These are the people that I am trying help out with this blog. Some problems require a little bit of back and forth, as in, "Try this." "I tried that and it didn't change anything."" Oh. well, you probably need to try that." " I tried that and it helped, but it still isn't quite right." "Now you need to try this...." If you go to http://www.allfordmustangs.com/ and then go to the classics forums, you will be able to do that with a pretty hefty gathering of some very knowledgeable people that also happen to be very friendly. None of that ridiculous one-upmanship, no flaming or abuse, none of that stuff. Just good, solid advice from people that know what they are talking about.

Friday, March 28, 2008

Electrical problem diagnosis

Hello. The electrical problems that your car might experience are generally not very complicated. The first step in figuring out how to fix the problem is to determine if there even is a problem. That might sound a bit odd, but I have seen many, many occassions in which someone was trying to fix a problem that didn't exist, so, first, find out if the car is supposed to be ' doing that' or not. The only tool that you will need, other than basic hand tools, will be a volt meter of some sort. Electrons flow, for all practical purposes, just like water. They need a place to come from, they need a place to go, and they need an unbroken path between those two places. Once you have determined that there is a problem with a particular system, you start at the battery and check with your volt meter for power all the way along the circuit until you find the kink in the flow. On electrical systems, the ground is the ' place to go'. A faulty ground connection can make electrical systems do all sorts of weird things, just bear in mind that extreme symptoms don't always indicate an extreme problem. Normally, on these cars, electrical problems result from either a failed component, like a signal flasher or voltage regulator, a ground connection that has gotten all corroded and funky-looking or a wire that has corroded or broken. You simply start at one end of the system and go through until you find the culprit. Intermittent problems, like headlights blinking out at bad times, are normally, but not always, the result of an ancient switch that just needs to be replaced. If jiggling something seems to be making something get better ( or worse) then whatever it is that you are jiggling is probably either the actual problem area or is attached to the problem area. It isn't rocket science on these cars. You can do this.

16 comments:

Thank you. That is very kind of you. I'll be adding stuff as it occurs to me. If you have something in particular that you are wondering about, please feel free to let me know. If I can't help you, I'll send you to someone that can over at allfordmustangs.

My first thought would be that either, A) One of the two wires on the brake switch has a bald spot on it, and when you step on the brakes it causes that bald spot to short out and blow a fuse, or, B) the wire sending power to the tail lights when you step on the brakes has that short in it. Which fuse is it that blows?

Have an interesting problem. I can't get my turn signals to work, and I've been all through the car looking for issues. The front left and rear right work, and the others don't. The parking lights work all the way around, so I do have juice to the wires, but the signals won't work on both sides!?

Using the exterior light schematic from your page, I see there's a black/yellow and white/blue line coming from the right side signal and two black/yellow and one green/white line coming from the right signal. I have positive power from the green/white wire on the left, but I have positive power from the black/yellow line on the right. Strange, because it appears the black yellow lines connect?

Do you know which wires should be positive and negative for each side? I have a new light kit that has a black, blue, and brown wire. Right now the blue is hooked up to + and the brown runs to the headlights, with the black going to the ground on each side.

Hi Tom. There should be three wires coming out of each of the front turn signal/ parking light assemblies. Each will have a black wire, which is the ground. Each will have a black/yellow wire, which is the one that supplies power for the parking lights, and the driver's side assembly will have a green/white wire, which supplies power for the left turn signal, and the passenger side assemblie will have a white/blue wire which supplies power to the right turn signal.

As far as what your problem might be, my first guess would be the bulb up front. It's a dual filament bulb, with power coming to it for the two different functions from two different places. For all practical purposes,it's two differnt light bulbs occupying the same space. The back bulb in the taillight housing could also just be the bulb It's also a dual filament bulb. I would turn on the taillights, step on the brakes and see if the light in question gets brighter when the brakes are applied. If no, that could also be a bulb.

I quadruple checked. The bulbs are good all the way around and the brake lights/parking lights work.

Any idea why I have positive juice in the green/white wire instead of the white/blue wire on the passenger side? I'm almost positive that before I started having these problems that the white/blue wire WAS the positive line...but now it has switched somehow. Strange I know...

The only wire on that assembly which is not positive is the ground wire. It would not be possible to get the green/white wire and the white/blue wires crossed up. Also, those two wires sahould never have constant power on either one of them. Those are the wires that power the turn signals. The power reading is supposed to be on/off/on/offf. etc... If either, or both of those wires is showing constant power, something is seriously wrong with the wiring. Try this. With the keys to car in your pocket, check and see if one of those wires is showing power. Then check the other one.If no to both, turn on the parking lights and check both of those wires again to see if they are showing power.

The good news is I have not + power in the wires when the car is off. The bad news is I have no power from the passenger side white/blue wire; the driver's side, front works as it should. I do have power in both parking light wires, so they both work. Still have break and tail lights in driver's rear, but no signal.

And I now have, for no known reason, a parasitic draw that drained a new battery; just happened out of the blue.

The latest I found is I do not have any power coming from the firewall connector for the right, front signal. At this point, I believe my signal switch has gone bad and am planning to replace. I also seem to have a bad alternator which seems to be the source of what I thought was a parasitic draw. As soon as I pull the negative cable off the battery, it immediately dies. Why I'm able to drive so far on just battery power is a mystery.

The car is supposed to die when you pull the negative cable. If, when you pull the positive battery cable, the car dies, that would mean that the alternator is not charging. The reason for that being that the car is supposed to be running off of the alternator, not the battery. Removing the negative battery cable is disconnecting the alternator's ground. Try starting the car and then disconnecting the positive battery cable and see how that goes.

I would be inclined to believe that the turn signal switch is indeed the problem here.I would first check the wire at the eight wire connector coming out of the steering column and see if I had power there before replacing the turn signal switch. If there's no power at the connector on the wire that goes to the light that isn't working, then, yes, it's probably the turn signal switch.

Good news. I replaced the signal switch and the lights all work perfectly. Hours and hours of work and it was the switch. My alternator issues were solved with a new $13 regulator switch. Thank you for all your help!

Nice blog! This post reminded me of the problems I had with a pair of new front parking lights on my '66, causing the passenger light to be full on with the parking lights, and the turn signal light in the dash to be illuminated too. Both were wired wrong from the manufacturer. I have a photo on my blog. http://66restomod.blogspot.com/2008/09/brand-new-repro-parts-adventures-in.html

That's why I don't use reproduction parts on my car. If I was going to re-cover the seats or something, I would have to use reproduction seat covers, I guess, but, if the part has electrical components or moving mechanical parts that have to actually do something, there's no way I'm putting that on my car. Especially Scott Drake's junk. It is my opinion that his products are of the lowest quality, virtually guaranteed to fail entirely straight out of the box.